The present invention relates to an electronic apparatus and, a method of cooling the same, and more particularly, to an electronic apparatus having heat-generating electronic parts which are cooled by using a liquid coolant and a method of cooling the electronic apparatus.
In recent years, as the technique for high-density packaging of integrated circuits boarded on an electronic apparatus has advanced, density of heat generated in the electronic apparatus has been increased. In this type of electronic apparatus, a liquid cooling system as disclosed in, for example, U.S. Pat. Nos. 4,226,281 and 4,800,956 has been employed in place of an air cooling system based on forced convection of air.
A prior art electronic apparatus employing the liquid cooling scheme will be described with reference to FIGS. 12, 13 and 14.
Referring in particular to FIG. 12, the electronic apparatus comprises a plurality of electronic computers 10, each carrying various integrated circuits, and a single cooler 20 which absorbs heat generated in the integrated circuits to cool them.
Provided in the cooler 20 are, as shown in FIG. 14, a primary coolant circulating line through which freon serving as a primary coolant circulates and part of a secondary coolant circulating line through which water serving as a secondary coolant circulates.
The primary coolant circulating line includes a compressor 21 for compressing freon, a condenser 22, a heat exchanger 23 for performing heat exchange between freon and water, and freon pipes 24 for interconnecting together the above components.
The secondary coolant circulating line in the cooler 20 includes a tank 25 for absorbing a change in volume of water, a pump 26 for pressurizing and feeding the water, and water pipes 27 for interconnecting together the above components.
Each electronic computer 10 includes, as shown in FIG. 14, a plurality of electronic circuit modules 11, each having integrated circuits formed on a substrate, cooling jackets 12, fed with water serving as the secondary coolant to cool the electronic circuit modules 11, water pipes 13 for feeding water to and discharging water from the cooling jackets 12, and piping paths 13a.
The water pipes 13 of each electronic computer 10 and water pipes 27 of the cooler 20 are interconnected together by flexible water pipes 19. The flexible water pipes 19 are laid under the floor as shown in FIG. 13 to meet requirements of working efficiency.
Water, warmed up by receiving heat transferred from the electronic circuit modules 11 through the cooling jackets 12, is led to the cooler 20 by the water pipes 13 and flexible pipe 19. Within the cooler 20, the warmed water is cooled by undergoing heat exchange with freon at the heat exchanger 23 in the secondary coolant circulating line, and the cooled water is pressurized by the pump 26 and again led to the cooling jackets 12 of the electronic computer 10.
As compared to the air cooling system, the above described liquid cooling system provides a significantly improved cooling power and is very suitable for cooling large-scale electronic apparatus. However, presently even medium-scale and small-scale electronic apparatus tend toward an increase heat generation density equivalent to the large-scale electronic apparatus and, in some medium-scale and small-scale electronic apparatus, a liquid cooling system similar to that of the large-scale electronic apparatus has been adopted.
However, when a liquid cooling system is employed for the medium-scale and small-scale electronic apparatus which is similar to the large-scale electronic apparatus, wherein the electronic computer and the cooler which are separately individual units, the following problems arise:
The medium-scale or small-scale electronic apparatus is often installed in an ordinary office room and reduction of installation space is one of its important performance factors. However, the arrangement in which the electronic computers and the cooler are disposed separately adversely affects realization of a realization of the installation space reduction and requires a sophisticated layout at the installation site.
Piping has to be laid between the electronic computers and the cooler and consequently installation is time-consuming. Especially when the installation site is in an ordinary office, it is preferable that installation be finished within as short a period of time as possible; however, it takes a long time to rearrange other office machines and, in any case, the office may be soiled.
Because of resistance between the electronic computers and the cooler, pumping power of a pump in the cooler has to be increased to make up for the piping resistance and accordingly the pump is increased in size and running cost is raised.
The electronic apparatus with the liquid cooling system faces a further problem in that, when the electronic apparatus of a liquid cooling system in non-operational for a long period of time, the coolant deteriorates and there is an increase in corrosion of the jackets and pipes ultimately resulting in requiring a draining of the coolant.
However, in the prior art electronic apparatus, a method for draining the coolant is not, in particular, considered and, even if a coolant drainage is effected in the construction shown in FIG. 14, the coolant in the flexible pipes 19 laid under the floor and in the piping paths 13a cannot be drained.
With a view of preventing this problem, a method has been proposed in which highly pressurized air is fed so as to remove the coolant in the cooling jackets; however, disadvantages to this proposed method resides in the fact that a compressor is required, thereby providing yet an additional component which requires maintenance and drainage becomes complicated.